The Arctic is among the most sensitive ecosystems to environmental and anthropogenic change, and therefore an ideal system in which to study how such changes impact the distribution and abundance of plant and animal species. Because environmental impacts are difficult to measure in real-time, our project aimed to measure how populations of Arctic mammals responded to environmental shifts that happened in the past. Our ultimate goal with this work was to provide new insights that can help make informed decisions about managing present-day populations that are affected by habitat loss and change. Focusing on horses that lived in the Arctic throughout the last 100,000 years, we used ancient DNA, or DNA that is preserved within the remains of organisms that used to be alive, to reconstruct the population history of horses across arctic Eurasia and North America. By estimating patterns of genetic diversity, this approach makes it possible for us to learn when horse populations were growing or declining, to detect local extinctions and replacements, and to track long-distance movements of horses, such as between Asia and North America across the sometimes-exposed Bering Land Bridge. Using these data, we estimated how changes in vegetation and available habitat altered the connectivity between horse populations, and how this impacted their genetic diversity and their long-term survival. We found that available vegetation and competition with other herbivores best predicted the abundance of ice age horses, which became extinct in North America during or after the transition from the last ice age into the warm Holocene of today. We also found that the ability to disperse between patches of useful habitat was key to maintaining genetic diversity in ice age horse populations. When horse populations were connected via habitat corridors, horses migrated between even very distant habitats, exchanged genes with populations that lived in these distant habitats, and maintained overall high levels of genetic diversity. When habitat became scarce, populations became isolated and lost genetic diversity, ultimately leading to their extinction in North America and across much of their previous range. Our results suggest that the maintenance of habitat connectivity will be crucial to sustaining populations today that are increasingly isolated by changes to their habitat due to human land use and other factors. 

In addition to contributing new genomic and radiocarbon data to the larger scientific community, our project has broader impact via the development of new technologies and human resources. Several postdoctoral scholars, three graduate students, and broad diversity of undergraduate students were trained cutting-edge experimental and bioinformatics approaches, as well as in the effective communication of science. We developed new technologies to recover ancient DNA that have been transferred from academia to industry, and created a new classroom resource for middle and high school students that explores the consequences of habitat change on large mammal populations. We trained two pre-service science teachers during the course of our project, and both have taken their skills and experience to schools that serve communities that are traditionally underrepresented in science. Finally, we created and implemented a new field-based undergraduate course in which 13 undergraduate students traveled to the North American Arctic to interact with working scientists and engage with local people. These students not only had first-hand experiences as professional scientists, but developed and practiced new skills in science communication through the creation of podcasts and participation in a live debate. Nearly all of these students are continuing their training in natural sciences, science communication, or as science teachers.

Last Modified: 03/14/2019
Modified by: Beth Shapiro